Many mobile phones on the market today provide phone functionality and also have a built in camera with flash capability in order to take higher quality photos. These phones may require circuitry that enables audio functionality for the phone and the flash capability. Audio functionality for a mobile phone is not just limited to the phone functionality but can also include the audio functionality for playing music, games, and videos and running applications and programs.
The camera flashes on mobile phones often use light emitting diode (LED) flash drivers to enable flash capability. The majority of these flashes for mobile phones are enabled through a boosted LED flash driver (e.g., having a boost converter). The boost converter is used for powering the LED driver and works to provide a constant current source. Generally, the flash driver uses a boost converter that works as a constant current source wherein the flash driver is enabled using hardware pins and is configurable via an I2C interface. Such an exemplary LED flash driver is disclosed in Analogic Tech Product Datasheet MT 1271 for 1.5 A Step-Up Current Regulator for Flash LED dated April 2009.
Also, mobile phones on the market today often use a boosted audio amplifier for higher and louder audio quality. A boosted audio amplifier comprises a boost converter powering an audio amplifier. By boosting the audio amplifier, the sound output of the amplifier may be increased and made louder. In addition, by boosting the voltage to a higher voltage level, the sound output may not be clipped by the battery voltage threshold because the audio amplifier will not be limited to the voltage supplied by the battery.
Different types of audio amplifiers exist. Such types of amplifiers include but are not limited to Class D, H, A, B, and A-B amplifiers. A boosted class-D amplifier may deliver a higher output power independent of the battery voltage because the boost can guarantee constant delivery of power to the audio amplifier. When a boost converter is used for powering a class-D amplifier, the boost converter works to provide a constant voltage source to the audio amplifier. In another case, a class-H scheme is implemented to maximize the boost converter efficiency by varying the boost output voltage at a certain signal level. At each respective signal level, the boost converter works to provide a corresponding constant voltage source. One disadvantage of the powering scheme for a boosted Class-D amplifier is that the overall system cost and size increase due to the requirements of additional components related to operating the boost converter with the audio amplifier.
Because both the LED flash driver and the audio amplifier require a similar or same type of boost converter, there is a desire and need for both the LED flash driver and audio amplifier to be supplied by a single boost converter.
FIG. 1 depicts an exemplary block diagram of an LED flash driver and audio amplifier power supply in accordance with the prior art in which a single boost converter is used to simultaneously drive both the LED flash driver and audio amplifier power supply. Such an exemplary circuit implementation is disclosed in Texas Instruments Datasheet for TPS61300, TPS61301, TPS61305 entitled “1.5 A/4.1 A Multiple LED Camera Flash Driver with 12CTM Compatible Interface” dated June 2009 and revised September 2010. Referring to FIG. 1, a constant DC voltage supply 102 may be coupled to a capacitor 104 and an inductor 106. Moreover, the inductor 106 may be coupled to an integrated circuit (“IC”) 108 that comprises a single boosted LED driver and controller. The boosted LED flash driver IC 108 may drive the LED flash light using another capacitor 110 and diodes 112, 114. The LED flash driver IC 108 may also drive an audio amplifier 124. The audio amplifier 124 may comprise a Class-D amplifier 120, two audio inputs 116, 118 and a speaker system 122 that outputs an audio signal. Control of LED flash driver IC 108 and audio amplifier 124 may be provided at the board level. Such control at the board level may be provided through system software that uses a General Purpose Input/Output (GPIO) port of the LED flash driver IC 108, or an I2C interface. Such control may involve the exclusive operation of either the LED flash driver IC 108 or audio amplifier 124, or operating the LED flash driver IC 108 and the audio amplifier 124 simultaneously. When operating simultaneously, the control may include reducing the gain of the audio amplifier 124. Because the audio amplifier 124 is external to the controller in LED flash driver IC 108, the audio signal level may not be monitored before the LED flash is turned on. Thus, the gain amount of the audio signal that needs to be attenuated is hard to determine, and in most cases, due to the high crest factor of music contents, a need to reduce audio gain may not even exist. Thus, the controller for the LED flash driver 108 may be limited to being used to control the audio amplifier 124.
Therefore, it may be desirable to provide a way to control both the LED flash driver and the audio amplifier by using a controller that is on a single integrated circuit. Such a solution is disclosed in U.S. Utility patent application Ser. No. 13/548,963 filed Jul. 13, 2012, and entitled “Chip Level Integration of a Boosted Class-D Amplifier and Integrated LED Flash Driver,” which is incorporated by reference herein in its entirety.
When a boost converter system is used to deliver power to multiple loads, a number of problems may occur due to limited battery capacity, inductor saturation, over-heating, and power delivery limitations of the boost converter. Traditional solutions typically focus on electrical overload protection by limiting the current of the boost converter or over-temperature protection by disabling the boost converter. With such solutions, typically no on-chip management of the boost converter load is attempted in order to maintain regulated operation within its maximum deliverable power and within its desired temperature range. Accordingly, it may be desirable to allow a user a choice to optimize audio quality, LED flash current, or both, and allocate power between boosted components based on such user preferences.